Percussion fuse for projectiles



Juiy4, 1939. M. BlRKlGT 2,164,797

PERCUSSION FUSE FOR fROJECTILES Filed Jan. 4, 1938 Z'g." 1a

INVENTOR ATTORN EYS Patented July 4, 1939 UNID Application January 4, 1938, Serial No. 183,344 In Belgium September 28, 1937 8 Claims.

The present invention relates to percussion fuses for projectiles, and it is more especially, although not exclusively, concerned with fuses for shells of small caliber.

The chief object of the present invention is to produce a percussion fuse of this kind which is better adapted to meet the requirements of practice than similar fuses used up to this time.

With this object in view, I make use of a fuse of the type in which the ignition of the primer is produced. by the sudden compression of a certain volume of air therein.

The essential feature of the present invention consists in devising such a fuse in a manner such that it includes, on the one hand, at the front part thereof, at least one compression chamber in which the rise of pressure that is to produce the ignition of the fuse primer is to take place, and, on the other hand, in communication with said first chamber, through a throttled passage, at least one other chamber in which said primer can be housed.

According to another feature of the present invention, relative to fuses in which the ignition of the primer is produced, when the projectile strikes an obstacle, by the sudden compression of a certain volume of air in a chamber provided in the nose of the fuse, I interpose, between said primer and the front part of the fuse, a closing device capable of protecting temporarily said primer against accidental pressure variations as may occur, said closing device being preferably locked so that it can be brought out of action only when the acceleration of the projectile along its trajectory has had its sign changed.

Still another feature of the present invention consists, while providing a fuse of the type above referred to with at least one closing device capa ble of protecting the explosive matters it contains against any accidental percussion actions, in constituting this device by a plurality of elements forming a screen when they are juxtaposed and tending to move away from one another under the action of the centrifugal force,

" these elements being kept assembled as long as necessary by suitable locking means, so as to remain in the position in which they constitute a protective screen.

Other resulting features of the present invention will appear from the following detailed description of a specific embodiment thereof.

A preferred embodiment of the present invention will be hereinafter described, with reference to the accompanying drawing, given merely by way of example, and in which:

Fig. 1 is an axial sectional view of a percussion fuse made according to a preferred embodiment of the present invention, the parts being in the position they occupy when the projectile has not yet been fired in a gun;

Fig. 2 is a View similar to Fig. 1, showing the parts in the position they occupy a short time after the projectile has been fired;

In the following description, it will be assumed that it is desired to obtain a pecussion fuse for a projectile of small caliber to be used in a gun having rifles.

I make use of the principle, already known in the art, which consists in ensuring the working of this fuse through the sudden rise of pressure which occurs in the fuse when the latter strikes an obstacle. As this compression can, for practical purposes, be considered as adiabatic, it produces a considerable rise of temperature capable of igniting the primer.

According to my invention, the percussion fuse includes the following parts:

a. On the one hand, at the front part, at least one compression chamber I in which the pressure rise can take place for ensuring the ignition of the primer 2 of the fuse;

b. On the other hand, in communication with said first mentioned chamber through at least one throttled passage 3, at least one other chamber 4 in which the primer 2 is housed.

In a specific manner, I may make use of the embodiment shown by the drawing and which is made as follows:

The chamber I in which the sudden compression is to take place, is obtained by making an axial bore in the body 5 of the fuse. This bore is chamfered at its front part so as to form a sharp edge 6 which facilitates the cutting of a round plug in the obstacle when the latter is struck. Eventually, this bore is closed at its front part by a thin cap I.

I provide, coaxially with hole I and behind it, another hole, which constitutes at least a part of chamber 4 and is prolonged rearwardly by a chamber 8 in which is housed the detonator 9, the primer 2 being fitted in the bottom part of chamber 4 ahead of said detonator.

If these chambers l and i are made to communicate together through a circular passage constituting the throttled part 3 above referred to, I obtain the arrangement above describe-d in a broad manner.

Throttle passage 3 can be provided either directly in the body of the fuse, or, as shown by the drawing, in a part of the safety device which will be hereinafter described.

It will be readily understood that, when the projectile strikes an obstacle, the plug cut off from said obstacle, for instance the cloth covering of an airplane wing, eventually associated with thin cap 1, acts as a piston in chamber I and produces a sudden rise of pressure in said chamber, as a result of the fact that the air present therein cannot escape freely through passage 3. Therefore a jet of hot air under high pressure will flow through said passage into chambend,

so that primer 2, located in said chamber will be ignited provided that it is made of a highly sensitive explosive, such for instance as lead,

triresorcinate.

Of course, it will be necessary to obtain, by suitably choosing the relatively volumes of chambers I and 4, that the amount of heat disengaged by the sudden compression taking place in chamber I should always be suilicient for ensuring the ignition of primer 2, the sensitiveness of the fuse depending, to a high degree, upon the ratio of these volumes.

It is also possible to act on this sensitiveness by varying the distance at which primer 2 is located from the throttled passage 3, or by suitably choosing the ratio of bore 1 and said throttled passage, this last mentioned ratio being preferably equal to 2.

A fuse made as above described is capable of giving very satisfactory results, but I consider that it is preferable to provide it with a safety device capable of protecting as long as necessary the explosive charge against percussion actions.

According to an important feature of the present invention, this safety device consists of a screen or the like normally interposed between the nose of the fuse and primer 2, said screen being preferably locked in this position so that it can be brought out of the way only when the sign of the acceleration of the projectile along its trajectory changes, so that the fuse cannot work until the projectile has moved to a certain distance from the muzzle of the gun.

In particular, in the case of a fuse such as that above described, it seems that it is particularly advantageous to have this screen coacting with the throttled passage 3, the section to be closed for separating the primer 2-from the external actions being, in this part, relatively small,

Although it is possible to make. use of many different embodiments of such a screen and of the. means. for keeping it locked up to the desired time (which will be supposed to be the time at which the acceleration of the projectile has its sign changed), it seems particularly advantageous to have recourse, for this purpose, to an arrangement according to the invention and which is applicable to any fuse requiring safety means of this kind, and according to which, the safety means include a plurality of elements forming a screen when they are juxtaposed and tending to move away from one another under the effect of the centrifugal force, these elements being maintained, up to the desired time, by suitable locking means, in their position in which they form the screen.

With object in I may, for instance, make use of, the arrangement disclosed by the drawing...

According to this arrangement, the screen is formed by two semi-circular shutters it and IE having frusto-conical lateral walls.

These shutters are carried by a kind of ring II, itself applied against a shoulder provided in the body of the fuse, the centralhole of said ring being located opposite throttled passage 3 and being separated from the latter by shutters I0 and I0 when they are juxtaposed along their respective diameters.

The locking means consist of a kind of sleeve I2 capable of sliding in chamber I against the action of a spring I3, which urges it against shutters I0 and ID, the lower part of said sleeve, in which throttled passage 3 is provided fitting exactly upon said shutters when the latter are located in adjoining relation.

The operation of such a safety device, then takes place in the following manner, the various elements thereof having been arranged, when mounted, as shown by Fig. 1, so that, in this position of. the parts, shutters it) and Hi are locked inv adjoining relation to each other by sleeve i2.

As soon as the shell is being expelled from the gun, the centrifugal force tends to move shutters I0 and I0 away from each other, but the considerable acceleration of the projectile applies sleeve I2 against said shutters and prevents them from moving away from each other.

When this acceleration ceases, that is to say a short time after the shell has left the gun, the pressure exerted by sleeve I2 decreases, or even disappears entirely. The action of the centrifugal force becomes preponderating, and shutters I0 and II) can move away from each other, compelling sleeve I 2' to move axially. Passage 3 is now cleared (position shown by Fig. 2) The fuse is now ready to Work as soon as it strikes an obstacle.

It will be readily understood that it is possible to adjust the safety thus obtained by acting upon the strength of spring I3 or on the mass of sleeve I2, or again upon the angle of the cone formed by the lateral walls of said shutters.

It is also possible, in order to improve the safety, to substitute for ring It a thrust ball bearing so that shutters I0 and it start rotating only after a certain delay.

Whatever be the embodiment that is chosen, the percussion fuse according to the invention as above described has considerable advantages, among which the following may be cited:

a. The construction of such a fuse is particularly simple, so that its operation is relaible and its cost relatively low;

from the nose of the fuse and well. protected by shutters I0 and I0 and an accidentalshock on the nose of said fuse does not risk causing the percussion of the fuse, as above explained.

' In a general manner, while I have, in the above description, disclosed what I deem to be a practical and efficient embodiment of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition, and form of the parts'wi'thout departing from the principle of the present invention as comprehended within the scope of the appended claims.

What I claim is:

1. A percussion fuse, especially for projectiles of small caliber, comprising a body having a first and a second chamber therein, passage means forming a restricted opening between said chambers, said first, chamber being adjacent the nose of said fuse sothat a Sudden rise of gas pressure occurs in said first chamber when said projectile strikes an object, a primer partially filling said second chamber and spaced from said restricted opening whereby gas compressed in said first chamber emerges as a jet through said restricted opening to impinge upon said primer.

2. A fuse as in claim 1, said chambers being spaced along a common axis, and said restricted opening being coaxial therewith.

3. A fuse as in claim 1, said nose of said fuse being chamfered and providing a cutting edge for the opening into said first chamber, and said chambers being axially aligned.

4. A fuse as in claim 1, a thin cap closing the opening of said first chamber at said nose of said fuse, said cap being adapted to act as a piston upon said gas in said chamber when said projectile strikes an object.

5. A fuse as in claim 1, said restricted opening having a diameter approximately one-half the diameter of said first chamber.

6. A fuse as in claim 1, an annular piece housed in said first chamber, said passage means comprising in part a restricted opening in said annular piece.

7. A fuse as in claim 1, safety means for closing the passage means between said chambers when the projectile is not being fired from a gun.

8. A fuse as in claim 1, safety means for closing the passage means between said chambers comprising a shutter openable under centrifugal force and a movable annular member forming a part of the unrestricted volume of said first chamber for locking said shutter in closed position during positive acceleration of said projectile.

MARC BIRKIG'I. 

